CODEWITHSUNDEEP
c++opencv
yusuf
yusuf

Reputation: 3781

"conversion from ‘IplImage* {aka _IplImage*}’ to non-scalar type ‘cv::Mat’ requested" error when using cvQueryFrame

I am trying to run the following code: 

#include <highgui.h>
#include <iostream>
#include <stdio.h>
#include <cv.h>

using namespace std;
using namespace cv;
using namespace std;

int main()
{
    cvNamedWindow("Brezel detecting camera", 1);
    // Capture images from any camera connected to the system
    CvCapture* capture = cvCaptureFromCAM(CV_CAP_ANY);

    // Load the trained model
    CascadeClassifier brezelDetector;
    brezelDetector.load("src/person.xml");

    if (brezelDetector.empty())
    {
        printf("Empty model.");
        return 0;
    }

    char key;
    while (true)
    {
        // Get a frame from the camera
        Mat frame = cvQueryFrame(capture); //----->>>>>>> This line

        std::vector<Rect> brezels;

        // Detect brezels
        brezelDetector.detectMultiScale(frame, brezels, 1.1, 30,
                0 | CV_HAAR_SCALE_IMAGE, Size(200, 320));

        for (int i = 0; i < (int) brezels.size(); i++)
        {
            Point pt1(brezels[i].x, brezels[i].y);
            Point pt2(brezels[i].x + brezels[i].width,
                    brezels[i].y + brezels[i].width);

            // Draw a rectangle around the detected brezel
            rectangle(frame, pt1, pt2, Scalar(0, 0, 255), 2);
            putText(frame, "Brezel", pt1, FONT_HERSHEY_PLAIN, 1.0,
                    Scalar(255, 0, 0), 2.0);

        }

        // Show the transformed frame
        imshow("Brezel detecting camera", frame);

        // Read keystrokes, exit after ESC pressed
        key = cvWaitKey(10);
        if (char(key) == 27)
        {
            break;
        }
    }

    return 0;
}

But I am getting "conversion from ‘IplImage* {aka _IplImage*}’ to non-scalar type ‘cv::Mat’ requested" error on this line:

Mat frame = cvQueryFrame(capture);

I am using opencv3. How can I fix this issue?

Thanks,

Upvotes: 1

Views: 4701

Answers (3)

Sagar Patel
Sagar Patel

Reputation: 852

  • First get image in IplImage like this:

    IplImage* image = cvQueryFrame(capture);

    then, 

    Mat matImage(image);

Upvotes: 0

Kornel
Kornel

Reputation: 5354

Well, I don't really advise to you to use the old/obsolete IplImage format, but the conversion into cv::Mat is possible as below:

cv::Ptr<IplImage> iplimg(cvQueryFrame(capture)); // cv::Ptr<T> is safe ref-counting pointer class
if(!iplimg)
{
    break;
}

// cv::Mat replaces the CvMat and IplImage, but it's easy to convert
// between the old and the new data structures (by default, only the header
// is converted, while the data is shared)
cv::Mat img = cv::cvarrToMat(iplimg);

Why don't you use cv::VideoCapture instead?

cv::VideoCapture cap(0); // open the default camera
if(!cap.isOpened())  // check if we succeeded
    return -1;

while(true)
{
    cv::Mat frame;
    cap >> frame; // get a new frame from camera

    cv::imshow("frame", frame);
    cv::waitKey(1);
}

Upvotes: 4

Siim Veskilt
Siim Veskilt

Reputation: 80

Try using the constructor:

Mat frame(cvQueryFrame(capture));

Or with newer OpenCV versions where the constructor has been removed:

Mat frame = cvarrToMat(cvQueryFrame(capture));

Upvotes: 1

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